Rust should be added in Implementation Language Vocabulary

[dbizeul]

rust is not listed currently

[rpiazza]

This is a good idea - but Implementation Language Vocabulary is an "open-vocab", which means other values are allowed, and the vocabulary in the specification can be thought of as suggested values to help with interoperability.

The concept of open-vocabs is to handle this exact situation, which is especially true for implementation languages, i.e., the suggested list is always underspecified.

However, in future specification versions commonly used values not already in the open-vocab should be added.

Therefore, adding rust makes sense.